Limb amputations have been a part of human existence since the earliest beginnings. While the reasons for such traumas vary and have changed over the centuries, limb amputations continue to account for a significant portion of major injuries each year. Currently, over 1.6 million people currently live with the loss of a limb and that number is expected to double by 2050. Over 30% of those people have lost a lower extremity. The difficulties of living and working with a prosthetic limb remain almost the same as they have from the earliest days. Various types of prosthetic limbs have been devised over time to assist individuals with lower limb amputations. Today's prosthetic limbs are highly sophisticated with a vast array of light-weight materials and ergonomic designs to facilitate normal walking patterns.
Notwithstanding all of the improvements to external prosthetic limbs, a lower-extremity amputee still faces the difficulty of being able to adjust to using a new prosthesis quickly. Some patients can take years to functionally adapt to a prosthesis. This is because, regardless of how many improvements are made to external prosthetic devices, they still operate by attachment to a residual limb having a blunt-ended terminal bone. For a non-amputee, the forces associated with ambulation are distributed throughout the musculo-skeletal system, particularly of the legs and feet. The joints between the bones, which contain a non-compressible fluid, act like hydrodynamic dampers or shock absorbers that absorb the kinetic energy associated with ambulation and distribute it throughout the musculo-skeletal system. For an amputee, the loss of one or more joints means that forces can no longer be adequately distributed and usually become intensified at the terminal end of the residual limb. With the loss of the fluid filled ankle joint in below-knee amputations and the loss of the knee joint and ankle joint in above the knee amputations, the normal non-compressible-fluid hydrodynamic system of the legs and axial skeleton is lost. As a result, expecting an amputee to walk on a boney stump inserted into a prosthetic socket can be unreasonable, as evidenced by the difficulty often experienced by amputees with transitioning to and using a new prosthesis. Thus, it is important to consider reconstruction of the hydrodynamic function of the skeletal system after amputation.
There is a need to overcome the dysfunctional, post-surgical, anatomical deficiencies exhibited by most currently used prosthetic devices. More specifically, there is a need for a system that replaces that portion of the non-compressible-fluid hydrodynamic system lost with amputation. Such a system should distribute the weight and forces of ambulation over a larger area of the residual limb end and reestablish the role of the axial skeletal system in ambulation. Ideally, such improvements will provide long term solutions and facilitate better use of a variety of external prosthetic devices.